1. Technical Field
The present invention relates to a display system having a display device that uses an electrophoretic phenomenon and a display method for the display device and the display system.
2. Related Art
Some of conventional nonluminescent display devices use an electrophoretic phenomenon (for example, refer to JP-A-2002-116733). Electrophoresis is a phenomenon in which when an electric field is applied to a dispersed system in which positively or negatively charged fine particles (electrophoretic particles) dispersed in liquid (dispersion medium), the electrophoretic particles migrate by Coulomb force. This display device has a display section in which a device substrate having pixel electrodes and a counter electrode having a common electrode are opposed at a specified interval, between which a dispersed system serving as pixels, a unit of image display, is disposed. The device substrate and the counter substrate are made of a transparent material. The dispersed system that constitutes pixels have, for binary representation (monochrome display), positively charged white electrophoretic particles and negatively charged black electrophoretic particles dispersed in liquid. Another example of the dispersed system contains white electrophoretic particles dispersed in liquid (dispersion medium) stained in black.
When a potential difference is applied between the pixel electrodes and the common electrode of such display devices, the electrophoretic particles are attracted from the initial position to the pixel electrodes or the common electrode by Coulomb force. At that time, if white electrophoretic particles are attracted to the transparent common electrode, light incident on the common electrode is reflected by the electrophoretic particles to allow the color (white) of the electrophoretic particles to be viewed. On the other hand, if black electrophoretic particles are attracted to the transparent common electrode, light incident on the common electrode is reflected by the electrophoretic particles to allow the color (black) of the electrophoretic particles to be viewed. In other words, these display devices are configured such that a common electrode and pixel electrodes are opposed in matrix form and the positions of the electrophoretic particles in the dispersed system between both electrodes are individually controlled so that images including characters and pictures are formed. Moreover, when power supply to the pixels is stopped, the electrophoretic particles of this display device are stopped at a position moved from the initial position, so that the display content can be held.
Such display devices are configured to erase held display content before new display content is written thereto. Methods for efficiently erasing the display content include erasing the display content by applying a potential difference opposite to that for display. However, the opposite potential difference to be applied to pixels is generated according to image data corresponding to the held display content. It is therefore necessary for the display device to have a high-capacity storage circuit capable of storing the image data corresponding to the held display content for a long period. Even with such a storage circuit, power is exhausted when the display device is carried for a long time, for example, so that the image data stored in the storage circuit is lost and therefore the display content cannot be erased efficiently.